The Impact of Non-Covalent Interactions on the Dispersion of Fullerenes and Graphene in Polymers

The work presented in this dissertation attempts to form an understanding of the importance of polymer connectivity and nanoparticle shape and curvature on the formation of non-covalent interactions between polymer and nanoparticles by monitoring the dispersion of nanoparticles in copolymers containing functionalities that can form non-covalent interactions with carbon nanoparticles.

The first portion of this study is to gain a fundamental understanding of the role of electron donating/withdrawing moieties on the dispersion of the fullerenes in copolymers. UV- Vis spectroscopy and x-ray diffraction were used to quantify the miscibility limit of C60 fullerene with the incorporation of electron donor-acceptor interactions (EDA) between the polymer and fullerene. The miscibility and dispersion of the nanoparticles in a polymer matrix are interpreted to indicate the extent of intermolecular interactions, in this case non-covalent EDA interactions. Experimental data indicate that the presence of a minority of interacting functional groups within the polymer chains leads to an optimum interaction between polymer and fullerene. This is further affirmed by density functional theory (DFT) calculations that specify the binding energy between interacting monomers and fullerenes.

The second portion focuses on the impact of sample preparation on the dispersion of graphene nanocomposites. Visualization and transparency are used to quantify the dispersion of graphene in the polymer matrix. In addition, differential scanning Calorimetry (DSC) also provides insight into the efficiency of the preparation process in forming a homogeneous sample, where rapid precipitation and solvent evaporation are studied. Examining the change in glass transition temperature, Tg, with nanoparticle addition also provides insight into the level of interaction and dispersion in the graphene nanocomposites.

The approach of utilizing non-covalent interactions to enhance the dispersion of polymer nanocomposites is realized by varying the functional group in the copolymer chains, while the impact of nanoparticle shape is also examined. The optimum enhancement of dispersion is interpreted in terms of the improvement of interaction between polymer and nanocomposites. This interpretation leads to the conclusion that chain connectivity and the ability of the polymer to conform to the nanoparticle shape are two important factors that govern the formation of non-covalent interactions in polymer nanocomposites.